1. Field of the Invention.
This invention relates to keyboards for electronic circuits and is concerned more particularly with a keyboard of the kind in which a key, when depressed, moves an elastomeric conducting element into contact with or in proximity to two conductive regions on a printed circuit element.
2. Prior Art.
In such a keyboard, the elastomeric member which may be a conductive elastomer or may carry a metal plate or metal/plastics laminate or otherwise be made conductive on or near its surface either makes a conductive (possibly resistive) connection or capacitive coupling between the two conductive regions on the printed circuit board. One such keyboard is described in application Ser. No. 161,611 of S. Zilkha, filed July 12th 1971 now U.S. Pat No. 3,797,630. It may be preferred in such an arrangement to provide a thin sheet of insulating material to form a coverlay over the conductive elements thereby ensuring that the coupling is capacitive. This eliminates many of the problems due to possible incomplete contact between the conductive elastomeric material and the conductive regions on the printed circuit board.